Schizophrenia (SCZD) is a debilitating psychiatric disorder. While 1.1% of the population suffers from SCZD, the molecular mechanisms underlying the disease state remain unclear. Though its characteristic symptoms typically appear late in adolescence, SCZD is believed to result from abnormal neurodevelopmental processes that begin years before the onset of symptoms. We previously reprogrammed fibroblasts from SCZD patients into human induced pluripotent stem cells (hiPSCs) and subsequently differentiated these disorder-specific hiPSCs into neurons; SCZD hiPSC neurons have reduced neuronal connectivity and altered gene expression relative to controls. Because gene expression profiles of our hiPSC-derived neural cells most resemble first trimester neural tissue, we believe that hiPSC neural cells are best used to study the embryonic developmental effects that contribute to disease initiation. Childhood-onset SCZD (COS) is a rare and particularly severe form of the disorder. Because COS patients present with symptoms much earlier than adult-onset cases of SCZD, our hypothesis is that neural cells derived from patients with COS will share cellular phenotypes with those we have already reported for adult-onset SCZD, but that the phenotypes may be accelerated and/or more severe. We believe that hiPSC studies of COS are an ideal platform from which to glean mechanistic insights into the early cellular and molecular factors responsible for disease initiation in SCZD. We have four primary goals for this BRAINS R01. First, we will generate hiPSC-based models of COS. Second, the cellular phenotypes of COS neural cells will be characterized across a panel of existing and validated assays. Third, mRNA and microRNA expression of COS neural cells will be integrated through causal network interference analysis in order to identify key microRNA regulators. Finally, we will begin mechanistic studies of candidate microRNAs altered in COS. We hope to use our novel hiPSC based platform to identify molecular insights into COS which may be generalizable across SCZD.